Hitherto, as the method of loading the chip-parts or the like on the substrate forming an electronic circuit, one method has been practiced which loads one after another the chip-parts of one kind, sent to a supply station and positioned thereat by a part supply device, onto the substrate by the use of a pick and place unit.
The conventional example will be described below with reference to FIGS. 1 through 5. In FIG. 1, 1 is a loader device for supplying a substrate 2 automatically, the substrate 2 prepared and placed on the loader device 1 being supplied onto an XY table 4 by means of a substrate conveying pawl 3 and oriented with respect both to an X direction and a Y direction orthogonal to the X direction. 5 is a chip-part loading device, and 6 is a linearly-reciprocatingly-movable chip-part supply section.
Now, the chip-part loading device will be described with reference to FIGS. 2 through 4. In these drawings, 10 is the chip-part placed on the chip-part supply section 6, and 11 is a vacuum nozzle to attract the chip-part 10, which is supported slidably by a shaft 13 via a compression spring 12. The shaft 13 is hollow and is connected through a tube 14 to a vacuum generating source. The shaft 13 is fixed to a shaft 15 which in turn is supported vertically slidably, and moves vertically in response to the movement of a cam 19 via levers 16, 17, 18. 20 is a cam coaxial with the cam 19, and 21, 22 are levers for drive transmission, coupled to a rack 23. 24 is a gear engaging with the rack 23, thus, in response to the crosswise movement of the rack 23 the shaft 13 performs a rotational motion about the shaft 15.
In the foregoing structure, the chip-part 10 on the chip-part supply section 6, after attracted by the vacuum nozzle 11, rises as indicated by the arrow A, moves laterally as indicated by the arrow B, and falls as indicated by the arrow C thereby to be loaded onto the substrate 2. During the foregoing steps, the movement of the vacuum nozzle 11 is controlled by the cam 19 through the shaft 13, shaft 15, levers 16, 17, 18 with respect to the vertical direction, and by the cam 20 through the gear 24, rack 23, levers 22, 21 with respect to the horizontal direction, so that the attracting, moving and loading of the chip-parts are carried out by the composition of motion in both directions.
FIG. 5 is a graph showing the displacement in the loading operation of the chip-part 10 and vacuum nozzle 11 for attraction of the chip-part, performed by the foregoing chip-part loading device, and the loading load. As illustrated in the graph of FIG. 5, the bottom dead point of the vacuum nozzle 11 responsive to the drive cap does not always accord with the substrate 2 due to a variation in thickness of the chip-parts 10 or warp of the substrate 2, thus, as shown by portion A in FIG. 5, an impact load caused by the compression spring 12 and exceeding a set load would be applied to the chip-part 10 irrespective of the vacuum nozzle 11 being urged by the compression spring 19. Further, as shown by portion B in FIG. 5, it was confirmed that the vacuum nozzle 11 exhibits jumping.
As apparent from the foregoing description, the chip-part loading method utilizing the cam drive mechanism had the drawback that the loading motion which should be high in accuracy and reliability can not answer to the thickness and the like of the object chip-parts because the extent of displacement of the cam is fixed. Accordingly, chip-parts able to be loaded were limited in thickness, and cracks would be generated in thin ship-parts. In addition, jumping and the like of the vacuum nozzle were the cause that the degree of accuracy on loading the chip-parts could not be increased sufficiently.
Furthermore, plural cams and motors therefor were needed, other than the movable portions for the vertical and horizontal motions, in order to achieve cam driving, thus, this made it difficult to miniaturize the device as a whole. Still, it was necessary to cause a cam follower to follow the cam, thus, there was the drawback that speedup of the motion could hardly be realized.